Electrostatic filters have been developed for incorporation into heating ventilation and air conditioning (HVAC) systems. Such filters, having the same general overall dimensions as a conventional panel-type filter element, can be placed into the duct of an HVAC system and oriented transverse to the direction of air flow in the duct. In general, electrostatic filters include a central charging screen that is sandwiched between two fibrous filter elements, and the filter elements and charging screen are enclosed between outer screens, each having a rigid frame surrounding a mesh material. Power is applied to the central charging screen which induces a particle-attracting charge in the filter elements, thereby providing improved filtration as compared to a non-electrified filter. Examples of such filter assemblies are described in the following United States patents, the respective disclosures of which are hereby incorporated by reference: U.S. Pat. Nos. 5,846,302; 5,807,425; 5,573,577; 4,828,586; 4,549,887; 4,886,526; 4,978,372; and 5,108,470.
Prior art electronic filters include clumsy latches or other hardware for holding the multi-piece filter assembly together. Such hardware protrudes from the frames of the outer screens and can get hung up on screws or rivets securing c-channels for holding the filter assembly within the duct of the HVAC system, thereby making the installation and extraction of the filter assembly difficult.
Accordingly, there exists a need for an electronic air filter assembly in which the filter assembly is securely held together in a manner which does not interfere with the duct work in which the filter is installed and in a manner which permits easy disassembly.
The present invention includes a multi-piece electronic filter assembly whereby the pieces are held together by pressure-activated securements that do not protrude or otherwise extend outside of the outer frames of the assembly. Accordingly, there are no structures or latches to get caught when the filter is installed in or removed from a duct. Moreover, the filter assembly can be disassembled by pulling the outermost pieces of the assembly apart with sufficient force to overcome the securements.
In another aspect of the invention, the overall particle attraction of the assembly is improved by the use of tackified filters.
Other objects, features, and characteristics of the present invention, including the methods of operation and the function and interrelation of the elements of structure, will become more apparent upon consideration of the following description and the appended claims, with reference to the accompanying drawings, all of which form a part of this disclosure, wherein like reference numerals designate corresponding parts in the various figures.